Lubricating oil composition



PatentedDec. is, 1945 LUBRICATING on. COMPOSITIOhl John G. McNab,Cranford, and Carroll J. Wilson and Carl Winning, Westfleld, N. 1.,asslgnors to Standard Oil Development Company, a corporation-of DelawareNo Drawing. Application December 31, 1941, Serial No. 425,130

7' Claims.

This invention relates to lubricating oils and methods of preparing thesame, and more particularly to mineral lubricating oil compositions foruse as crankcase lubricants in internal combustion engines.

Because in recent years the requirements for lubricating oils forgasoline and Diesel engines have steadily been made more stringent, ithas been proposed to add various ingredients to these oils to improvetheir behavior in such service.

One purpose of these ingredients is to immrt detergency to the oils,thus bringing about greater engine cleanliness and avoiding ringsticking, carbon formation and varnish deposition. Certain of theseingredients also impart oxidation resistant properties to oils, therebytending to inhibit the development of corrosive ingredients in suchoils. Corrosion-preventing addition agents are particularly requiredwhen the oil is to come in contact with the newer type of alloys ofsilver and cadmium and of copper and lead, which are now widely used asbearing metals.

Various metal containing organic compounds, particularly metal salts,exhibit detergent properties by inhibiting the formation of varnish,lacquer, and sludge deposits and in promoting general cleanliness in theengine, and a very valuable class of such salts is the metal salts ofinorganic acids having substituent oil-solubilizing organic groups. Forexample, salts of substituted orthophosphoric acids, such as calciumcetyl phosphate, calcium (cetyl phenyl) phosphate, aluminum octadecylphosphate, and chromium oleyl phosphate, and the cadmium, tin, andcobalt mahogany sulfonates are among those been disclosed as additionagents.

While the above described metal salts are uniformly satisfactory asdetergent agents, they vary somewhat in their ability to preventcorrosion, and some even increase the corrosive properties of the oilwith which they are blended. Moreover, in the use of the salts theeffectiveness of these compounds is gradually spent. The detergentcapacity becomes exhausted as deterioration products, soot, dirt,varnish, etc., accumulate in the lubricant and saturate the adsorptivepower of the additive. In engines equipped with a iiiter, the lattertends to remove the additive, particularly when the additive is adsorbedon co'ntamination products which are strained out by the filter. Theoxidation processes which are unwhich have derway in an oil during iiseoperate upon the antioxidant functions or theadditi-ve and thus alsocontribute to its exhaustion. The oxidation of the oil also createsinsoluble substances which the. detergent is called upon to absorb, thuslessening its capacity for dispersing contamination products which enterthe oil, and acidic substances are also formed which may react directlywith the detergent to destroy its efllcacy. When the detergent isemployed also to impart corrosion resistantproperties to the oil, theabove degrada tion phenomena all hasten to break down this corrosionresistance.

It is an object of this invention to provide an ingredient which, addedto the metallic detergent, will provide the continued corrosioninhibiting efiect desired. Such a ingredient is an alk'ylation productof p-cresol, as defined more particularly in the description whichfollows. bination of addition agents provides for detergent action inthe earlier stages of the use or the oil as well as continued corrosioninhibiting eiiectafter the metallic detergent compound has been removedto some degree by the filter or otherwise weakened in its action.-Furthermore, the presence of the second additive prevents any positivecorrosive action by the metal compound, which may have been selectedparticularly because of its effective detergent action.

The present invention consists, then, in the use in mineral lubricatingoils of a combinationof two additives. the first being a metallic saltofan inorganic acid having at least one substituent oil-solubilizingorganic group and the second being an alkylated reaction product ofp-cresol, as defined in the description which follows.

The salts used in the lubricating compositions of the present inventionmay, in general, be any metallic salts of inorganic acids containing atleast one organic group which serves'to render the salt soluble inmineral oil. This organic group may appear as a substituent for one ofthe hydrogen atoms of the. inorganic acid from which the salt wasderived, or the group may even appear as a substituent for a hydroxylgroup of such acid, as in the case of salts of organic sulfonic acidswhich may be considered as sulfuric acid in which one hydroxyl group issubstituted by an organic group. Since there must be at least one metalatom or equivalent radical and at least one soiubllizing organic groupin the salt, such This com- .product in white oil manufacture,tetradecyl phosphoric acid (C14H:0O(OH):PO), 'naphthenyl phosphinicacids, hexadecyl tetrathlophosphoric acid (CuHsaS(BH) :PS). dodecylmonothio ester of phosphoric. acid (CnH2cS(OH) 3P0), dicetyl ester ofmonothio phosphoric acid (CrcHsaO) :(OH) PS] decyl monothio ester ofpropyl phosphonic acid (CmHnS(OH) (Cam) P) octadecyl esterof butylphosphonic acid (CuH31O(OH)(C4Hs)PO), diisobutyl diphenoxy sulfide esterof phosphoric acid,

whichin its simplest form may be represented as I Ci uJhHI amyl benzylsulfurous acid (C5H11CsH4CH2O) (OH) S0] and dioctyl sulfamlc acid['(c'mnmmmson. as well as comparable substituted arsenic, arsenious,arsinic, aisonic, boric, stannic, stannous,

chromic, chromous, plumbous, plumbic, aluminic' and silicic acids andthe like, also the corresponding acids in which sulfur, selenium ortellurium is substituted for oxygen. Included also are the derivativesof the above named acids in which halogen, oxygen, nitrogen and sulfursubstituents I appear in the orEaZno group. Especially preferredsalts-are the phosphates and thiophosphates, also sulfates andsulfonates, particularly those derived from petrole nn.

In the foregoing discussion, as well as elsewhere in this aieciilcation,the diisobutyl radical formin: part of various compoimds is to beunderstood as being a derived from. diisobutylene, and such radical mayalso be designated as tetramethyl butyl.

The metals which may appear in the salts which are added to the minerallubricating oils may be any metals, and the salts may include salts ofamines, pyridine and similar basic nitrogen compounds, ammonium (NH4-)or salts of ammonimn containing one to four substituent organicradicals, such as the quaternary ammonium salts, and the correspondingsalts of phosphonium, sulfonium, arsonium, and stibonium bases.Espercialiy preferred are the'metalsof groups I, II, III, IV and VIII ofthe periodic table. Salts of group H, such as magnesium, calcium, andbarium salts, have been found to be particularly effective.

- 1 whenpolyvalentmetalsareused. their valences may be satisfied withlike radicals as depicted above or the metals mar be joined to diilerentradicals, as, for example, in the following com-Alsomixturesofsaltsmaybeusedmforexample, calcium diisobutylphenylphosphite and barium octadecyl phosphate.

' The substituted inorganic salts to be added to lubricating oils inaccordance with this invention include the following: calcium cetylphosphate, barium oleyl phosphate, aluminum lauryl phos phate, bariumdi(amvlphenyl) thiophosphate, chromium octadecyl phosphate, barium cetylphenyl phosphate, barium wax phosphate (in which the wax radical isderived from wax), calcium dioctyi dithiophosphate, and the magnesium,ring-cobalt, calcium, barium and The oil-solubilizing substituentorganic group which appears as part of the salt structure may beofanytype, providing only that itimparts appreciable oil solubility tothe salt. Thus. the substituent groups may be alkyl, alkoxy, aryl,aralkyi or heterocyclic groups, and such groups may, furthermore.atoms,-for example, amino, nitro, hydroxy or 'mercaptan groups, orhalogen atoms. I

Typical of the metallic salt compounds preferred for use inaccordsnce'with the present invention are the following, which areillustrated by structural formulas showing the structures tin salts ofmahogany acids (petroleum sulfonic acids) More particularly preferredare zinc dioctyl monothiophosphite, calciumdioctyl monothiophosphite,barium dioctyi monothiophosphite, the zinc and barium salts of mahoganyacids, calcium diisobutyl phenyl phosphate and calcium cetyl phosphate.

The substituted inorganic may be prepared in various ways. method, suchas that described in U.

One typical 8. Patent No, 2,228,659, consists in reacting an appropriatecontain substituent groups and inorganic oxide or sulfide, for example,an oxide or an aliphatic alcohol sulfide of phosphorus, with I inorganicacid, which is subsequently reactedwith an alkali to form thedesired-metal salt is formed by precipitating alkali salt on adding theappropriate metal ion.

In the case of the preparation of salts of sulfonicacidasuchasthecalciumorbariumsaltaalkali salts of suifonic acids,well-known as emulsifyinl which a few of the most preferred compoundsare 76 agents and obtained fractions or petroleum I salts describedabove froma solution of the other hydrocarbon materials, by -means wellknown to the art, may be reacted in appropriate solutions with calciumor barium salt to form the corresponding calcium or barium soaps of thesulfonic acid.

The second additive which is to be introduced into the lubricating oilcompounds in accordance with the present inventionis a product obtainedby alkylating p-cresol with a tertiary alkyl group in the presence of asuitable alkylation catalyst. The source of the tertiary alkyl group mayb a tertiary olefin, e. g., isobutene. A satisfactory method for thepreparation of one of the preferred additives consists in reactingp-cresol with isobutene in the presence of sulfuric acid as a catalystat about 70 C., in accordance with the method of preparation describedbelow in Example 4. The product has a molecular weight of about 220, achemical composition corresponding to the empirical formula C15Ha4O, andis, when purified, a white crystalline solid having a melting point ofabout 69.2 to 69.4 C.

The lubricating oil base stocks of this invention may be straightmineral lubricating oils or distillates derived from parailinic,naphthenic, asphaltic or mixed base crudes or, if desired, variousblended oils may be employed as well as residuals,

particularly those from which asphaltic constitu-- ents have beencarefully removed. The oils may be refined by conventional methods usingacid, alkali and/or clay or other agents such as aluminum chloride, orthey may be extracted oils produced, for example, by solvent extractionwith solvents of the type of phenol, sulfur dioxide, furfural, dichloroethyl ether, propane, nitrobenzene, crotonaldehyde, etc. Hydrogenatedoils or' white oils may be employed as well ,as synthetic oils prepared,for example, by the polymerization of oletrated compounds, and the like,may also be employed.

Assisting agents which are particularly desirable are the higheralcohols having 8 or more carbon atoms and preferably 12 to 20 carbonatoms. The alcohols may be saturated straight and branched chainaliphatic alcohols such as octyl alcohol, CaHnOH, lauryl alcohol,C12H25OH, cetyl alcohol, CmHasOH, stearyl alcohol, sometimes referred toas octadecyl alcohol, CIBHB'IOH, and the like; the correspondingolefinic alcohols such as oleyl alcohol; cyclic alcohols, such asnaphthenic alcohols; and aryl substituted alkyl alcohols, for instance,phenyl octyl alcohol, or octadecyl benzyl alcohol Or mixtures of thesevarious alcohols, which may be pure or substantially pure syntheticalcohols. One may also use mixed naturally occurring alcohols such asthose found in wool i'at (which is known to contain a subfins or .by thereaction of oxides of carbon with hydrogen or by the hydrogenation ofcoal or its products. In certain instances cracking coil tar fractionsand coal tar or shale oil distillates may also be used. Also, forspecial applications, animal, vegetable or fish oils or theirhydrogenated or voltolized products may be employed, either alone or inadmixture with mineral oils.

For the best results, however, the base stock chosen should usually bethat oil which without the additive present gives the optimumperformance in the service contemplated. Since one advantage of the.additives is that their use also makes feasible the employment of lesssatisfactory mineral oils or other oils, no strict rule can be laid downfor the choice of the base stock. Certain essentials must of course beobserved.

. The oil must possess the viscosity and volatility,

characteristics known to be required for the service contemplated. Theoil must be a satisfactory solvent for the additive, although in somecases auxiliary solvent agents may be used. The lubricating oils,however they may have been produced, may vary considerably inviscosity-and other properties depending upon the particular use forwhich they are desired, but they usually range from about 40 to 150seconds Saybolt vis- 'cosity at 210 F. For the lubrication of medium andhigh speed Diesel engines the general practice has been to use alubricating oil base stock prepared from naphthenic or aromatic crudesand having a Saybolt viscosity at 210 F. of to 90 seconds and aviscosity index of 0 to 50. However, in certain p s!!!- Diesel service,and in gasoline engine service, oils of higher viscosity index are oftenrequired, for example, up to 75 or 100, or even higher, viscosity index.

stantial percentage of alcohols having about 16 to 18 carbon atoms) andin sperm oil (which contains a high percentage of cetyl alcohol) andalthough it is preferable to isolate the alcohols from those materials,for some purposes the wool fat, sperm oil or other natural products richin alcohols may be used per se. Products prepared synthetically bychemical processes may also be used, such as alcohols prepared by theoxidation of petroleum hydrocarbons, e. g. paraflln wax, pets rolatum,etc.

Generally, the amounts of the substituted inorganic salt and of thealkylated p-cresol prod uct to be used in the compositions of thepresent invention should be between the approximate I limits of 0.02 and2.0%, and preferably from 0.1 to 1.0% of each ingredient, the exactamount to be used depending to a certain extent on the particularcompounds used, the character of the mineral oil base and the operatingconditions of the engine in which the lubricant is to be employed.

The following are typical lubricating oil compositions suitable for, usein internal combustion engines in accordance with this invention.

Oil A:

Mid-Continent base oil (S. A. E. 20) plus 1.0% barium octadecylphosphate, and 0.25% tert. butyl ether of o-tert. butyl p-cresol Oil B INaphthenic base oil (S. A. E. 30), plus 0.2% zinc dioctylmonothiophosphite, and

0.3% tert. butyl ether of o-tert. butyl p-cresol Oil 0: 1

Highly refined Mid-Continent base oil (S. A.

E. 20), plus 1.0% calcium diisobutylphenyl phosphate,-

and

0.25% tert. butyl ether of o-tert. butyl D-cresol Compositions in whichtwo or more metal compounds are med with one or more p-cresol productsor in which one metal compound is used with two or more p-cresolproducts are also contemplated in this invention.

In the following examples there are described in detail methods ofpreparing a number of the Exams: 1

Preparation of calcium octill thiophosphate A mixture of- 444 grams orphosphorous pentasulflde, 1170 g ams or octyl alcohol, and 250 grams ofsodium carbonate was heated gradually to 70 C. and finally to 110 C.with agitation until evolution or carbon dioxide and hydrogen sultidehad ceased. The reaction mixture was ill-- tered and then diluted with500 cc. of absolute ethyl alcohol. nitrate in 1 liter of ethyl alcoholwas added and the mixture filtered to remove the sodium nitrate formed.The ethyl alcohol was removed from the filtrate under vacuum and theresidue diluted with 1.5 liters oi petroleum ether and again filtered toremove the unreacted calcium nitrate.

The latter filtrate was contacted with metallic mercury to remove activesulfur as mercuric sulflde and again filtered The'petroleum ether wasstripped from the product and the latter was heated to l35-140 C. under3-4 mm. pressure for about 30 minutes to remove unreacted octyl alcohol.

Exmu: 2

Preparation of barium octyl thiophosphate 520 grams or octyl alcohol(2-ethyl hexanol) and 222 grams oi. powdered phosphorous Dentasulfidewere placed in a reaction flask and heated to 80 C. with agitation.Evolution of hydrogen sulfide began at about 50 C. and the r630? tionwas practically complete after 3-4 hours at 80 C., but the mixture 'wasagitated at 40-50' C. overnight with a slow stream or air passingthrough the flask. Titration of the crude product showed that 90.2% 01'the theoretical amount of octyl thiophoephoric acid,

(OIHIIOXP/ had iormed. The crude product was illtered toremove unreactedphowhorous pentasulilde, and 392 grams of the filtrate (containing 1 molor 354 grams or octyl thiophosphorlc acid) were neutralized withalcoholic sodium hydroxide; After removing the alcohol under vacuum, 422grams of a clear, straw colored. rather viscous oil were obtained. 75grams or the sodium octyl thiophosphatc thus formed were dissolved in150 cc. of absolute alcohol. A mixture oi 100 cc. or the alcohol and 36grams of barium bromide was added with stirring. The alcohol was removedby evaporation and the residue dissolved in ether and filtered. Uponremoval of the ether from the filtrate 63 grams or a straw colored.semi-solid material (barium octyl dithiofliosphate) were obtained.

A solution of 2 mols of calcium asogooo was 8 Preparation of barium soapor mahogany acids For the preparation or this compound a commerciallyavailable alcoholic solution of sodium salts of mahogany sulfonic acidswas employed. containing 12.75% of salts, 2.25% or mineral oil. and57.9% of isopr pyl alcohol; the remainder being water. To 400 grams ofthis solution was added an aqueous solution of 25 grams of bariumchloride. The mixture was boiled with stirring for one hour andthenevaporatedto dryness. The residue was taken up with 250 cc. of amixture of one part of naphtha to one part of a solution containing 60%of isopropyl alcohol and 40% of water. by volume. The naphtha layer wasseparated and washed free of chlorides with water. Evaporation of thenaphtha yielded 77 grams of barium sulionates which contained about ofmineral all remaining from the original alcohol solution.

Exams: 4

324 grams of technical p-cresol and 16 grams of 95.5 to 06% commercialsulfuric acid were agitated at 10C. in a suitable reaction vessel whileisobutene was bubbled through the mixture.

After about four hours the reaction was substantially complete, asindicated by the flow oi isobutene from the gas exit of the reactionvessel. The reaction mixture was then blown withsteam and washed withhot water and then with dilute alkali until neutral. The crude product(89% yield) was an oily material which readily crystal- 0 crystallizedfrom hot alcohol, it was obtained in are form of white crystals meltingat 89.2 to

In addition to being employed in crankcase lubricants for Diesel andautomotive engines, the additives oi the present invention may also beused in lightmineral oils such as spindle oils and textile oils, metalcutting oils, turbine oils, insulating and transformer oils, steamcylinder oils and greases. Also, since these additives achieve theirdetergent client by modifying surface activity, their use in asphalt,road oils, and waxes to improve wetting and adhesive properties is alsocontemplated. Likewise, they may be added to liquid fuels to increasetheir wetting ability for metals, enabling themto displace moisturewhich might otherwise cause corrosim fitkcontainers. tuel lines.pumpparts.andthe The present invention is not to be considered so aslimited by any otthe' examples described herein, which are given by wayof illustration only.

'but'istobelimitcdsolelybythetermsotthe appended'claims.

- We claim:

l. A lubricant comprising a major proportion of a mineral oil basestock, about 0.02% to about 2.0% of a salt oi. a polybasic inorganicacid which contains at least one oil-solubilizing substituent 1 organicgroup. said salt being a. salt or a metal selected fromgroupsI.II.IlI,IVandVl'lIotthe periodic table and having a. tendency to causecorrosion of metal surfaces during use in said lubricant, and about0.02% to about 2.0% of an alkylation product obtained by reactingp-cresol 76 with isobutene in the presence or a catalytic lized whencooled. when the product was re-' amount of sulfuric acid, said producthaving a molecular weight of about 220, a chemical compositioncorresponding to the empirical formula 015K240, and being, whenpurified, a white crystalline solid having a melting'point of aboutmelting point of about 692 to 69.4: C.

3. A lubricant comprising a major proportion of a mineral oil basestock, about 0.2% to" about 2.0% of. zinc dioctyl monothiophosphite, andabout 0.2% to about 2.0% of an alkylation prodnot obtained by reactingp-cresol with isobutene in the presence of sulfuric acid as a catalyst,said product having a molecular weight of about 220, a chemicalcomposition corresponding to the empirical formula CiaHaO, and being,when purifled, a white crystalline solid having a melting point 01'about 89.2 to 69.4 C.

4. A lubricant comprising a major proportion of a mineral oil basestock, about 0.2% to about 2.0% of calcium diisobutylphenyl phosphate,and about 0.2% to about 2.0% of an alkylatlon product obtained byreacting p cresol with isobutene in the presence of sulfuric acid as acatalyst, said product having a molecular weight of about 220, achemical composition corresponding to the empirical formula 015K240, andbeing, when purified, a white crystalline solid having a melting pointof about 69.2 to 69.4 C.

5. A lubricant accordingto claim 1 in which the metal salt is a salt ofa metal of group II of the periodic table.

6. A lubricant according to claim -1 in which the metal salt is a saltof a metal of group H of the periodic table and a petroleum mahoganysulfonic acid.

7. A lubricant according to claim 1 in which the metal salt is a salt ofa metal of group II of the periodic table and an acid of phosphoruscontaining an oil-solubilizing alkyl group.

JOHN G. MCNAB. CARROLL J. WILSON. CARL WINNING.

